Hydronics refers to the use of water as a heat transfer medium in heating and cooling systems. Hydronic systems are commonly utilized in heating, ventilating and air conditioner (HVAC) applications. Typical hydronic systems include a circulating heat transfer medium loop, associated valves, a radiator, a pump, and a boiler or chiller to implement the desired heat transfer. A water loop hydronic system also must include at least one expansion tank to accommodate a varying volume of the heat transfer liquid, such as water, inasmuch as the liquid volume contracts and expands as it cools and heats. The expansion tanks utilize an elastomeric diaphragm pressurized with compressed gas such as air to accommodate the variations in liquid volume by further gas expansion or compression, and help control pressure in the hydronic system.
Expansion tanks usually include a diaphragm to hold the excess liquid and a compressed gas portion for controlling over-all system pressure. When the diaphragm is overexpanded due to an excessive system pressure or a gas leak from the tank, the diaphragm can burst necessitating a costly system shut-down for repair. It would be advantageous to detect not only system failures such as a rupture of the diaphragm but also a condition wherein the diaphragm has been overly expanded and is likely to burst unless remedial steps, e.g., reduction in system pressure by draining, are timely taken.
Accordingly, it is an object of the present invention to provide an expansion tank having excessive diaphragm movement alarm means mounted thereto for monitoring expansion of the diaphragm within the expansion tank.
The term “diaphragm” as used herein and in the appended claims denotes an elastomeric deformable web or membrane that spans the tank and is secured to the sidewall of the tank (FIG. 8) or an elastomeric bladder suspended in the tank (FIG. 2) and adapted to hold a liquid. In either case, the web or membrane, as well as the bladder, partitions the tank interior into two compartments or portions—a closed, gas-containing portion for the containment of a gas under pressure and a liquid-containing portion for the holding of a portion of the liquid that expands from the system.
It is a further object of this invention to provide an expansion tank system and method of use which includes an expansion detector that does not damage the diaphragm in the expansion tank.
It is also an object to provide an expansion tank having a sensor element which is able to detect potential diaphragm failure modes, i.e. tank flooding and/or over-extension of a tank diaphragm.
It is yet another object to provide an expansion tank alarm system in module form so that it may be readily installed or replaced through a tank coupling.
These and other objects and advantages of the apparatus and method aspects of the present invention will be apparent to those skilled in the expansion tank art.